The prior art discloses various methods that are used in a data network to specify how data packets are forwarded from a source node to a destination node via intermediate network nodes. Particularly in the case of data transmission using the Internet protocol on the L3 layer of the OSI reference model, routing methods for forwarding IP data packets are known. The rules for forwarding are calculated by a routing protocol, such as the Open Shortest Path First (OSPF) method. By virtue of the interchange of signaling messages, the information about the topology of the data network is distributed in the data network, and each network node separately calculates the shortest path to each other network node or networks connected thereto on the basis of metrics or costs that have been allocated to the links between adjacent network nodes.